1. Field of the Invention
The present invention relates to a correction of earth magnetic field for a monitor of a computer, and more particularly, to an apparatus for automatically correcting an earth magnetic field for a monitor by which a correction of an earth magnetic field is automatically performed to thereby obtain a highly improved picture quality with distinct colors and an improved screen centering.
2. Description of the Background Art
In general, a magnetic field in a space is represented by a three dimensional vector, which affects a deflection of a monitor of a computer.
Accordingly, if a direction of the monitor is changed or the monitor is moved to other area, a peripheral magnetic field is changed, causing a damage to the picture quality of the monitor.
In order to resolve such a problem, some techniques for correcting an earth magnetic field has been proposed, which guarantees a distinct picture quality of the monitor
Of those are a Korean patent publication No. 96-16849 and a Korean Laid Open No. 95-24598.
First, one of conventional arts, the patent publication No. 96-16849 discloses an apparatus for correcting an earth magnetic field including: a standby power supply unit 11 for outputting a constant voltage Vcc as power is supplied; a remote controller 20 for setting an operation state of a TV system and selecting an earth magnetic field correction mode; a remote-controller receiving unit 19 for receiving a transmission signal of the remote-controller 20; a pre-amplifier 18 for amplifying the output signal from the remote-controller receiving unit 19 to a predetermined level; a microprocessor 15 for decoding the output signal from the pre-amplifier 18 and outputting an on-screen display indicating a compass direction of a corresponding mode for setting a correction mode and a signal for controlling the corresponding mode when the earth magnetic field correction function is selected, upon receipt of the output Vcc from the standby power supply unit 1; a chroma unit 16 for indicating the compass direction according to the setting of the correction mode of the CPT (color picture tube) upon receipt of the output signal from the microprocessor 15; a current switching unit 14 for switching on and switching off a current flow of a device coil 12 according to a relay drive signal S1 of the microprocessor 15; and an earth magnetic field correction unit 17 for controlling the direction and the strength of the current according to mode signals S3-S5 of the microprocessor 15 to minimize influence of the earth magnetic field.
The current switching unit 14 includes a transistor Q1 and a relay RY1.
The earth magnetic field correction unit 17 includes transistors Q7 and Q8 of which an emitter is grounded through resistances R10 and R13 and a base is connected to output terminals S3 and S5 of the microprocessor 15 through resistances R11 and R14, a transistor Q2 of which an emitter is grounded and a base is connected to an output terminal S4 of the microprocessor 15 through a resistance R2, transistors Q3, Q4, Q5 and Q6 of which each base is commonly connected to a terminal at one end of each resistance R3 and R4 and each emitter is commonly connected and an earth magnetic field correction coil L2 and a condensor Cl are respectively connected between the contact points, transistors Q3 and Q5 of which collectors are commonly connected and its contact point is connected to a voltage B+through a resistance R7 and the collector of the transistor Q7 and a terminal at other end of the resistance R3 are commonly connected through the resistance R9, and a collector of the transistor Q8 is connected to a terminal at the other end of the resistance R4 and its contact point is connected to the voltage B+through the resistance R12, and transistors Q4 and Q6 of which collectors are commonly connected and its contact point is grounded through a resistance R5, a resistance R6 is connected to the collector of the transistor Q2 through a resistance R6.
The remote-controller 20 includes a compass to identify a direction of the TV position, for the purpose of correcting the earth magnetic field.
The operational process of the apparatus for correcting an earth magnetic field in accordance with the conventional art will now be described with reference to FIGS. 2 through 4.
First, when the power is ON, the standby power supply unit 11 outputs the constant voltage Vcc to the input terminal S2 of the microprocessor 15, and accordingly, the microprocessor 15 in a standby state checks the output signal of the pre-amplifier 18.
At this time, when the power key is in an OFF-state, the microprocessor 15 outputs the relay drive signal S1 to the current switching unit 14 to turn off the transistor Q1 to thereby turn off the relay RY1, and also outputs the earth magnetic field correction signals S3-S5 of low voltage to maintain OFF-state of the system.
And, when a power key is inputted from the remote-controller by the user, the transmission signal of the remote-controller 20 is received by the remote-controller receiving unit 19, and the received signal is amplified by the preamplifier 18 to a predetermined level and then outputted to the microprocessor 15.
Upon receipt of the output signal from the pre-amplifier 18, when the microprocessor 15 discriminates the input of the power supply key by decoding and outputs the relay drive signal S1 to the current switching unit 14, the transistor Q1 is turned on to drive the relay RY1, according to which the contact points xe2x80x98axe2x80x99 and xe2x80x98bxe2x80x99 are connected and power is supplied to the power supply unit 13, so that the device coil 12 controls the current flow.
In other words, when the power is ON, a current flows through a thermister TH and the coil L1 of the device coil 12, and as time goes by, since a resistance value is increased according to temperature characteristics of the thermister TH, and thus, few current flows through the coil L1, the magnetic field of the monitor is degaussed.
Meanwhile, when the power is ON, the microprocessor 15 discriminates whether or not the earth magnetic field correction key was selected. In this respect, if there is no key selection, it returns to the initial step of the operation, while if the earth magnetic field correction key is selected by the remote-controller 20 by the user, the microprocessor 15 senses the key input through the remote-control receiving unit 19 and the pre-amplifier 18 and performs decoding. The microprocessor discriminates the selection of the earth magnetic field correction function by this decoding.
As the microprocessor 15 discriminates the selection of the earth magnetic field correction function by decoding the output signal from the preamplifier 18, it outputs a compass direction indication signal OSD to the chroma unit 16. Then, an on-screen display is displayed on a CPT (color picture tube) screen, and the user selects a corresponding key of the remote-controller 20 after ascertaining a direction of the TV position by using the compass attached on the remote-controller 20, so that a mode corresponding to the direction of the TV set position can be set by shifting the earth magnetic field correction mode one step by one step.
That is, as the user presses down the earth magnetic field correction mode setting key of the remote-controller 20 after ascertaining the direction of the TV position, the microprocessor 15 outputs the on-screen display signal OSD of the corresponding mode to the chroma unit 16, so that the on-screen display according to each mode is sequentially displayed on the screen of the CPT In this respect, at the time when the on-screen display identical to the direction of the TV position as identified by the compass attached on the remote-controller 20 is displayed, the user selects a set key to set a corresponding mode.
For example, if the TV set is turned aside 30xc2x0 (xe2x80x98Axe2x80x99 direction) from a standard direction, the earth magnetic field setting an on-screen display direction is set to be xe2x80x98Axe2x80x99 direction after the earth magnetic field correction mode is selected.
When the setting of the earth magnetic field correction mode is completed, the microprocessor 15 outputs the earth magnetic field correction signals S3, S4 and S5 according to the corresponding modes as set, to the earth magnetic field correction unit 17.
In detail, in case that the direction of the TV set position is identified as a standard direction and xe2x80x98Mode0xe2x80x99 is selected, since the microprocessor 15 outputs only earth magnetic field correction signals S3 and S5 of high voltage to the earth magnetic field correction unit 17, the transistors Q7 and Q8 are turned on while the transistors Q3 and Q5 are turned off. Then, since the current does not flow through the earth magnetic field correction coil L2, earth magnetic field correction is not performed.
Meanwhile, in case that the direction of the TV set position is identified as xe2x80x98Axe2x80x99 direction and xe2x80x98Modelxe2x80x99 is selected, since the microprocessor 15 outputs only the earth magnetic field correction signal S3 of high voltage, the transistors Q4, Q5 and Q7 of the earth magnetic field correction unit 17 are turned on, so that a little current flows in the xe2x80x98Axe2x80x99 direction (that is, B+xe2x86x92R7xe2x86x92Q5xe2x86x92L2xe2x86x92Q3xe2x86x92R5), thereby correcting the degaussed state.
If the earth magnetic field correction mode is changed to be set by xe2x80x98Mode2xe2x80x99 from xe2x80x98Mode1xe2x80x99, the direction of the TV set position is identified as a xe2x80x98Cxe2x80x99 direction, so that the microprocessor 15 outputs the earth magnetic field correction signals S3 and S4 of high voltage. Then, the transistors Q2, Q4, Q5 and Q7 of the earth magnetic field correction unit 17 are turned on, so that the current flowing through the resistance R5 also flows through the resistance R5 and the transistor Q2, thereby increasing the amount of the current (the flow of current: B+xe2x86x92R7xe2x86x92Q5xe2x86x92L2xe2x86x92Q4xe2x86x92R6xe2x86x92Q2).
If the earth magnetic field correction mode is set by xe2x80x98Mode3xe2x80x99, the direction of the TV set position is identified as the xe2x80x98Cxe2x80x99 direction, so that the microprocessor 15 outputs the earth magnetic field correction signals S4 and S5 of high voltage. Then the transistors Q2 and Q8 are turned on, and thus, the transistors Q3 and Q6 are accordingly turned on, according to which a large amount of current flows in the xe2x80x98Bxe2x80x99 direction (B+xe2x86x92R7xe2x86x92Q3xe2x86x92L2xe2x86x92Q6xe2x86x92R6xe2x86x92Q2), thereby correcting the degaussed state.
If the earth magnetic field correction mode is set by xe2x80x98Mode4xe2x80x99, the direction of the TV set position is identified as a xe2x80x98Dxe2x80x99 direction, so that the microprocessor 15 outputs only the earth magnetic field correction signal S5 of high voltage. Then, the transistor Q8 of the earth magnetic field correction unit 17 is turned on and the transistors Q3 and Q6 are accordingly turned on, so that a little current flows in the xe2x80x98B; direction (B+xe2x86x92R7xe2x86x92Q3xe2x86x92L2xe2x86x92Q6xe2x86x92R5)
The state of the earth magnetic field correction unit 17 at the time when the microprocessor 15 outputs the earth magnetic field correction signals S3-S5 according to setting of the earth magnetic field correction mode is shown in FIG. 3.
That is, in this example of the conventional art, the earth magnetic field correction mode is selected depending on the direction of the TV set position, and according to which when a corresponding mode is set, the earth magnetic field is automatically corrected, thereby providing images of distinct colors.
Meanwhile, as another example of a conventional art shown in FIG. 5, the Korean Laid Open No. 95-24598 discloses a deflection correction apparatus of a cathode ray tube which includes a correction amount determining unit 110 having correction amount signals corresponding to each direction and outputting each correction amount signal; a direction sensing and selecting unit 120 for sensing a direction of the cathode ray tube and selectively outputting one of correction amount signals inputted from the correction amount determining unit 110 according to the sensing result; and a deflection correction unit 130 for correcting a deflection of the cathode ray tube according to the correction amount signal outputted from the direction sensing and selecting unit 120.
The direction sensing and selecting unit 120 includes a direction sensor for outputting a sensing result signal; and an output selecting switch for selectively outputting the correction amount signal of the correction amount determining unit 110 according to the sensing result signal.
The operation of the a deflection correction apparatus of a cathode ray tube according to the conventional art will now be described.
First, correction amount signals according to each direction are stored in the correction amount determining unit 110 at the time when the monitor is fabricated.
When an earth magnetic field correcting mode is set at the time when the monitor is placed, the direction sensor of the direction sensing and selecting unit 120 senses the direction of the cathode ray tube, and the output selecting switch selects a signal corresponding to the sensing result amount correction amount signals outputted from the correction amount determining unit 110 and then outputs it to the deflection correction unit 130.
Then, the deflection correction unit 130 corrects the deflection of the cathode ray tube corresponding to the correction amount signal selectively outputted from the direction sensing and selecting unit 120, thereby providing a good quality of distinct color image.
However, as to the former conventional technique as described above, since the direction of the area for the placement of the monitor is to be first identified by the compass and then the earth magnetic field correction mode is selected corresponding to the direction as identified, many correction mode data need to be stored for correcting the earth magnetic field precisely, resulting in that it requires a large memory which inevitably causes an increase of a unit cost of production.
Also, as to the latter conventional technique as described above, since the earth magnetic field is different in each area, it has the same problem as that of the former conventional technique to correct the earth magnetic field for each area.
Therefore, an object of the present invention is to provide an apparatus for automatically correcting an earth magnetic field for a monitor in which a screen is automatically corrected by sensing a peripheral magnetic field with a small memory capacity, thereby attaining users"" convenience in correcting an earth magnetic field and maintaining an optimum picture quality.
To achieve these and other advantages and in accordance with the purposed of the present invention, as embodied and broadly described herein, there is provided an apparatus for automatically correcting an earth magnetic field for a monitor including: a peripheral magnetic field sensing unit for sensing a variation of a magnetic field and generating a corresponding frequency; a frequency producing unit for arithmetically operating the frequency generated from the peripheral magnetic field sensing unit and producing frequencies of each direction; a correction amount computing unit for computing each correction amount corresponding to each frequency of each direction produced by the frequency producing unit; and a deflection correction unit for correcting a deflection error of the monitor as much as the corrected amount in the correction amount computing unit.
The correction amount computing unit converts the frequency of the frequency producing unit to a magnetic field value according to a pre-stored frequency-magnetic correlative equation, and compares it with a pre-set reference magnetic field value to thereby compute a correction amount corresponding to a difference thereof.
The correction amount computing unit includes a microprocessor having a programmable memory in which a frequency-magnetic field correlative equation and a magnetic field-screen change correlative equation are stored to correct a tile, a vertical position, a horizontal position and a purity landing, and a storing unit (EEPROM) for storing an initial screen data and a reference magnetic field value of each direction.
There is also provided a method for automatically correcting an earth magnetic field for a monitor including the steps of: setting reference magnetic field values corresponding to three axes of X, Y and Z; measuring a magnetic field of the directions of the three axes; discriminating whether or not the reference magnetic field value in the reference magnetic field value setting step and the measured magnetic field in the magnetic field measuring step are identical to each other; maintaining a tilt, a vertical position, a horizontal position and a purity if the reference magnetic field value and the measured magnetic field in the discriminating step are identical; and determining a correction amount by using a predetermined equation and correcting a tile, a vertical position, a horizontal position and a purity if the reference magnetic field value and the measured magnetic field value in the discriminating step are not identical.